$4lm + 2m + 2n + 4 = 3m - 4n + 5$ Solve for $l$.
Answer: Combine constant terms on the right. $4lm + 2m + 2n + {4} = 3m - 4n + {5}$ $4lm + 2m + 2n = 3m - 4n + {1}$ Combine $n$ terms on the right. $4lm + 2m + {2n} = 3m - {4n} + 1$ $4lm + 2m = 3m - {6n} + 1$ Combine $m$ terms on the right. $4lm + {2m} = {3m} - 6n + 1$ $4lm = {m} - 6n + 1$ Isolate $l$ ${4}l{m} = m - 6n + 1$ $l = \dfrac{ m - 6n + 1 }{ {4m} }$